Lightly grind the peppercorns in a mortar in pestle so they’re in smaller pieces, but not as fine as a powder. Combine the ground peppercorns, five spice, chili flakes and salt in the melted butter and whisk together.
Combine corn and wheat Chex with peanuts, almonds and pretzels.
While the butter mixture is still warm, toss the mix with the butter and toss to evenly coat as much as possible. Spread on a baking sheet until butter is cool.